2-tert-butyl-4-chloro-5 -(4-tert-butylbenzylthio)-3(2H)-pyridazinone for controlling snails and slugs

ABSTRACT

Snails and slugs are controlled by a method in which the plants to be protected from molluscs, or the environment of the said plants, are or is treated with 2-tert-butyl-4-chloro-5-(4-tert-butylbenzylthio)-3(2H)-pyridazinone I ##STR1## Snail and slug baits or seed dressings contain the active ingredient I.

The present invention relates to a method for controlling molluscs, inwhich the plants to be protected from molluscs, or the environment ofthe said plants, are or is treated with2-tert-butyl-4-chloro-5-(4-tert-butyl-benzylthio)-3(2H)-pyridazinone I##STR2##

Snails and slugs are major pests in temperate, subtropical and tropicalcrops. For various reasons, for example because of quarantineregulations (Parella, M.P., Robb, K. and Morishita, P.: Calif.Agriculture 1985, Jan./Feb., 6-8), snail and slug control is becomingincreasingly important.

EP-A-134 439 discloses that2-tert-butyl-4-chloro-5-(4-tert-butylbenzylthio-3(2H)-pyridazinonepossesses, inter alia, excellent insecticidal and acaricidal properties.This publication does not indicate any molluscicidal action of thissubstance.

It is an object of the present invention to provide a novel agent and amethod for controlling snails and slugs.

We have found that this object is achieved and that an effectivepreparation against snails and slugs, for example one which can beformulated as a broadcasting agent, is obtained according to theinvention by using the 3(2H)-pyridazinone derivative I defined at theoutset.

The 3(2H)-pyridazinone derivative I has excellent molluscicidalproperties in the case of both slugs and snails and is very suitable forsnail and slug control in agricultural and horticultural crops.

The 3(2H)-pyridazinone derivative I can be prepared as described inEP-A-134 439.

Suitable formulations for molluscicides are described in, for example,GB-A-2 087 723, EP-A-190 595, DE-A-35 03 608, DE-A-37 06 358 and DE-A-3500 468. They generally contain a carrier, an edible substance or a lure,a binder and the active ingredient and, if required, conventionaladditives, such as preservatives, colorants, repellents, water, organicsolvents, surfactants and the active ingredient.

Examples of suitable (solid) carriers are ground natural minerals, suchas kaolins, aluminas, talc, chalk, quartz, attapulgite, montmorilloniteor diatomaceous earth, and ground synthetic minerals, such as finelydivided silica, alumina and silicates; examples of suitable solidcarriers for granules are crushed and fractionated natural minerals,such as calcite, marble, pumice, sepiolite, dolomite, synthetic granulesof inorganic and organic meals and granules of organic material, such assawdust, coconut shells, corn cobs and tobacco stalks.

The edible substances present may be any conventional feed substancewhich can be used in baits of this type. Ground cereals, for examplewheat flour, shredded wheat and shredded barley, as well as coarsesoybean flour, bran, rice starch, fish meal, meat meal and molasses, arepreferred. It is possible for only one edible substance or a mixture ofa plurality of edible substances to be present.

All conventional adhesives which can be used for such purposes may bepresent as binders. Methylcellulose, sugar, dextrin, starch, alginates,glycols, polyvinylpyrrolidone, ligninsulfonate, gum arabic, polyvinylalcohol and polyvinyl acetate are preferred. One or more binders may bepresent.

Examples of preservatives, which may or may not be present, are2-hydroxybiphenyl, sorbic acid, p-hydroxybenzaldehyde, methylp-hydroxybenzoate, benzaldehyde, benzoic acid, propyl p-hydroxybenzoateand p-nitrophenol.

Examples of colorants which are suitable additives for repelling birdsand mammals are inorganic pigments, such as iron oxide, titanium dioxideand Prussian blue, and organic dyes, such as anthraquinone, azo andmetal phthalocyanine dyes.

Substances used for attracting soil pests may be any conventionalcomponents suitable for this purpose. Aniseed and aniseed oil areexamples.

Repellents used for repelling warm-blooded animals, such as dogs andhedgehogs, may be any conventional components suitable for this purpose.Examples are nonanoic acid vanillylamide.

Suitable organic solvents are all organic solvents which can beconventionally used for the preparation of baits. Low boiling organicsolvents, such as methanol, ethanol, butanol and methylene chloride, arepreferred.

Suitable surfactants are nonionic substances, such as condensates ofpolyalkylene oxides and alkylphenols and fatty acid polyoxyalkyleneesters, for example octylphenoxypolyoxyethanol, cationic substances,such as quaternary ammonium salts, eg. cetyltrimethylammonium chlorideor cetylpyridinium chloride, and anionic substances, such as the sodiumsalts of the long-chain alkylsulfates, eg. sodium laurylsulfate, saltsof alkylarylsulfates, the sodium salt of desoxycholic acid, the sodiumsalt of taurocholic acid and the sodium salt of tauroglycocholic acid .

Another preferred form of application is seed dressing using aformulation usually employed for dressings.

The content of active ingredient in the individual application forms mayvary within wide limits, for example from 0.001 to 90, in particularfrom 0.5 to 50, preferably from 1 to 10, % by weight in the case ofgranular formulations and from 10 to 90% by weight in the case of seeddressings.

The application rate of active ingredient I is in general about 0.3-30,preferably 1-10, kg/ha.

The molluscidal action of the novel agents covers terrestrial andamphibious snails and slugs, for example those of the genera Deroceras(Agriolimax), Limax, Helix, Helicogona, Cepaea, Milax, Lymnaea (Galba),Achatina, Theba, Cochlicella, Helicarion and Vaginulus. The snail andslug pests include, for example, the slugs Arion ater, A lusitanicus, A.hortensis, Agriolimax reticulatus, Limax flavus, L. maximum, Milaxgagates, Mariella dursumierei, Helicarion salius, Vaginula hedleyi andPamarion pulillaris and the snails Helix aspersa app., Cepaea nemoralis,Theba pisana, Achatina fluica, A. zanzibarica, Bradybaena spp.,Cochlodina spp., Helicella spp. and Euomphalia spp.

FORMULATION EXAMPLE 1

2 kg of2-tert-butyl-4-chloro-5-(4-tert-butyl-benzylthio)-3(2H)-pyridazinone, 8kg of calcium stearate, 0.2 kg of sodium benzoate, 20 kg of chalk, 0.5kg of a blue dye and 63.3 kg of wheat bran were mixed in a mixer. Thismixture was then moistened with sufficient water in a kneader andkneaded. The moist mixture was then molded in an extruder to give snailand slug bait granules having a diameter of 3 mm, which were dried atnot more than 60° C.

FORMULATION EXAMPLE 2

To prepare a seed dressing,

480 g of2-tert-butyl-4-chloro-5-(4-tert-butylbenzyl-thio)-3(2H)-pyridazinone,

20 g of commercial phenolsulfonic acid/urea/formaldehyde condensate,

40 g of ethylene/propylene block copolymer having a molecular weight of10,000,

2 g of xanthan gum,

0.5 g of Rhodamine FB,

80 g of 1,2-propylene glycol and

5 g of silicone antifoam

where mixed, and the mixture was made up with water to 1 liter.

EXAMPLES OF USE

5 slugs were placed in each Petri dish (diameter 94 mm) and a lettuceleaf (=1 g) which had been dipped in an active ingredient solution ofthe stated concentration beforehand was added. All experiments wereplaced in a conditioned chamber at 20° C. and with an L/D (light/darkness) cycle of 18 : 6 hours. After 4 days, the mortality of theslugs was determined.

The test results are summarized in Tables A and B.

                  TABLE A                                                         ______________________________________                                        Arion hortensis (garden slug)                                                 2-3 cm body length                                                                       Concentration                                                      Compound   %           Number of dead slugs                                   ______________________________________                                        I          0.1         5                                                                 0.04        5                                                                 0.02        5                                                                 0.01        5                                                      Untreated  --          0                                                      ______________________________________                                    

                  TABLE B                                                         ______________________________________                                        Deroceras reticulatum (field slug)                                            2-3 cm body length                                                                       Concentration                                                      Compound   %           Number of dead slugs                                   ______________________________________                                        I          0.1         5                                                                 0.04        5                                                                 0.02        0                                                                 0.01        0                                                      Untreated  --          0                                                      ______________________________________                                    

We claim:
 1. A method for controlling mulluscs which comprises treatingplants to be protected from molluscs, or the environment of said plants,with a molluscicidally effective amount of a composition containing asolid carrier, an edible substance capable of attracting molluscs and,as a molluscicidal agent, an effective amount of2-tert-butyl-4-chloro-5-(4-tert-butylbenzylthio)-3(2H)-pyridazinone ofthe formula I: ##STR3##
 2. The method of claim 1, wherein about 0.3 to30 kg/ha of the compound of the formula I is applied.